The objectives of the proposed project are 1) to examine the stages of vocal development in normal infants and 2) to find out how each stage relates to its predecessor and to succeeding stages of vocal development. The vocal behaviors of the infants will be studied in terms of a descriptive feature-analysis system which is applied to individual segments of infant sounds and to suprasegmental features. The system is capable of detecting changes in segment features occurring with age and also of detecting new combinations of features. Those features which span groups of segments, i.e., the temporal organization of segments in series and and the fundamental frequency contour of those series, will be studied in the proposed project by means of acoustic measurements. The ability of both suprasegmental features and segmental features to characterize stages of vocal development will be tested. At a later date, if the attempt to characterize vocal development stages is successful, we will examine the situational contexts in which characteristic vocal behaviors are produced and the nonvocal behaviors which accompany the characteristic vocal behaviors. The project is designed to obtain information for use in assessing speech and language skills in young language-delayed children; and in planning procedures for the treatment of language delay in these children.